The phonetic alphabet developed by Zhou Youguang, pinyin, turns 50 this month, having helped up to a billion Chinese citizens to learn to read, write and in many cases speak the national language.

The 102-year-old linguist is renowned as the "father of pinyin", the system for representing standard Mandarin in the Roman alphabet. The country is celebrating the anniversary with lectures, a TV series and educational programmes.

Although Zhou is marking the half-century by publishing the latest of his many books, he is otherwise modest about his achievements and a life so packed with incident that for many years he completely forgot a brief friendship with Albert Einstein.

"I'm not the father of pinyin - I'm the son of pinyin," says Zhou."It's [the result of] a long tradition from the later years of the Qing dynasty down to today. But we restudied the problem and revisited it and made it more perfect."

The results are remarkable. Over the last half-century, the illiteracy rate in China has slumped from 80% to as little as 10% - the precise figure is disputed - thanks to a combination of mass education, simplified characters and pinyin.

"[Pinyin] is very simple but had a significant purpose. First, it denotes the sound of Chinese characters," Zhou explains.

"Second, it has helped [students] to learn putonghua, the national standard language. Before, I met a Cantonese and a Hokkien in foreign countries and couldn't communicate - I had to speak English to them. Without an alphabet you had to learn mouth to mouth, ear to ear. It's a bridge to speech between Chinese people."

Chan Yuen Chi, associate professor at the School of Chinese, Hong Kong University, argues that pinyin succeeded because it was a better phonetic match than other transcription methods, and was "extremely easy and convenient" because it used a widely recognised alphabet rather than other symbols.

"On a level of practicality, it makes up for the fact that Chinese characters do not indicate the sounds themselves," he says.

"In politics, economics and every kind of cultural work, it has very important value. China is a country of many dialects, and hanyu pinyin helps the realising of a common language for the entire nation."

Zhou's involvement came about by chance. He was a banker working in New York when the communists seized power in 1949 and, like many expatriates, he returned home to help rebuild his country.

"We all thought that China had a very good opportunity to develop; we didn't expect the later turmoil. History misled us," he says.

It soon became clear that his economic expertise was not required or appreciated. But in 1955 the government asked him to put his hobby - languages - to use by overseeing reforms. It believed only an explosion in literacy could allow China to develop.

Two years later, the unwanted career change saved him when Mao Zedong launched his anti-rightist campaign against intellectuals.

"Mao disliked greatly the economists - especially economic professors from America. By that time I had shifted to the line of language and writing. I was not considered a rightist. Very lucky," Zhou recalls.

"If I had remained in Shanghai teaching economics I think I certainly could have been imprisoned for 20 years. A good friend of mine was imprisoned and committed suicide; my student committed suicide."

However, he was denounced as a reactionary academic during the Cultural Revolution in the late Sixties, and exiled to the countryside.

Zhou, who still produces a paper a month from his modest flat in Beijing, is cheered to see that pinyin is growing ever more useful.

Many people rely on pinyin-to-character conversion programmes to send text messages or type on their computers and even Chinese Braille is based on the system.

But many students forget pinyin once they have reached their ultimate goal.

"Pinyin is not to replace Chinese characters; it is a help to Chinese characters," Zhou says.

"They have a very long tradition of more than 3,000 years ... people will use them for at least 500 years more. It's almost impossible to change to another writing system because it's so deeply rooted in China."

Nor does he believe that Mandarin will overtake English as the major international language, despite China's growing power and his own surprise at the number of foreigners learning putonghua.

"Chinese characters or pinyin will never be a competitor to English. [Its dominance] is the work of over 400 years," he added.

Background

Chinese languages do not have an alphabet. Instead they have a character for each word, which does not indicate pronunciation (although it sometimes contains a phonetic element).

The resulting difficulty in learning to read and write - or learning putonghua, standard Mandarin, if not a native speaker - has led to numerous attempts to develop phonetic representation systems.

The first attempts to transcribe Mandarin in the Roman alphabet were designed by foreigners seeking to learn Chinese; the best-known - though not the first - is Wade-Giles, produced and refined by two British diplomats in the second half of the 19th century.

The Chinese subsequently produced their own phonetic alphabet, Zhuyin, also known as Bopomofo after its first letters. Then came Gwoyeu Romatzyh, a romanisation system that spelled the tones as well as the sounds of words - but proved so complicated that few could master it.

The communists turned to Zhou Youguang and his team to develop a replacement that could establish standard Mandarin as a truly national language and increase literacy.

Chinese children who grow up speaking putonghua use pinyin to associate characters with spoken words. Those who grow up with other languages also use it as a guide to putonghua pronunciation.

Confusingly, Taiwan uses several different romanisation methods - including a variant of pinyin, tongyong pinyin - and zhuyin. Attempts to enforce a single system have proved highly controversial.

· This article was amended on Monday February 25 2008 as a result of a subediting error. In Chinese, family names come first so we should have referred to the linguist Zhou Youguang as Youguang, his given name as his family name. This has been changed.